1. Field of the Invention
This invention relates to the interiors of load centers for electric power distribution systems and includes a locking member for securing bus bars to the interior that can be used interchangeably with interiors with different current ratings, and therefore, different size bus bars.
2. Background Information
Load centers are used to distribute electric power to a number of branch circuits in a distribution system and to provide overload/overcurrent protection for those branch circuits. These functions are performed by what is known in the industry as an interior mounted inside an electrical enclosure. The interior includes a back pan secured to the rear wall of the enclosure. Mounted to the back pan is an electrically insulative support member supporting a pair of bus bars, each connected to an incoming line. The bus bars are mounted vertically side by side with stabs projecting from confronting edges interleafed in vertical alignment. The back pan has flanges along each side with vertically spaced notches that are engaged by the housings on miniature circuit breakers. The circuit breakers have a terminal that engages a stab to complete the mechanical connection of the circuit breaker to the interior and to electrically connect the protected branch circuit to a bus bar through the circuit breaker. The load center also includes terminals connecting the neutral conductors of the branch circuits to an incoming neutral line.
Typically, the support member of the interior is molded of an electrically insulative resin. In one arrangement, the bus bars seat in lateral slots formed in the vertical sides of the support member and are retained in place by sawtooth cleats molded on the support member to extend into the slots and engage openings in the bus bars. It is common for the bus bars to be connected to the incoming wiring by screw terminals. In the described arrangement, torque applied to the terminal screw to connect or disconnect the bus bar to or from the incoming wiring can cause the bus bar to disengage from the cleats and rotate out of the slot in the support member.
There is a need, therefore, for an improved load center with an arrangement that precludes the bus bars from rotating relative to the support member of the interior as the terminal screws are tightened or loosened.
This need and others are satisfied by the invention, which is directed to a locking member that firmly secures the bus bars in the support member of the interior of a load center, and to a load center interior incorporating such a locking member.
The load center of the invention comprises, in general, a back pan and an electrically insulative elongated support extending along the front face of the back pan. The elongated support has a lateral slot extending along at least one side, and at least one inwardly facing abutment surface positioned laterally inward of this at least one side. An elongated bus bar is seated in the lateral slot in the elongated support and has an outwardly facing edge and a plurality of spaced apart stabs extending forward from adjacent an inner edge. At least one locking member has a first locking surface facing laterally outward and engaging the inwardly facing abutment surface on the elongated support, and a second locking surface facing laterally inward spaced outward of the first locking surface and engaging the outwardly facing edge of the at least one bus bar to retain the bus bar in the lateral slot in the elongated support. The outwardly facing locking surface on the locking member can be defined by a groove in a locking member body. Also, the inwardly facing locking surface on the locking member that engages the outwardly facing edge on the bus bar can be formed by a forward extending flange on the locking member body.
In accordance with another aspect of the invention the elongated support comprises a longitudinally extending wall section forming the abutment surface engaged by the locking member.
In one embodiment of the invention, the elongated support has another lateral slot extending along another side edge in which is seated another bus bar. Another locking member secures this additional bus bar in the support member in a similar fashion.
In accordance with another aspect of the invention, a single locking member is structured for use with either of one load center interior and another load center interior, the one load center interior having one back pan, and one elongated support mounted on the back pan and having one lateral slot extending along one side and one laterally inwardly facing abutment surface. This one load center further includes one elongated bus bar seated in the one lateral slot and having one outer side edge and one width. The another load center interior comprises another back pan and another elongated support mounted on the another back pan and having another lateral slot extending along another side and another laterally inwardly facing abutment surface. Another elongated bus bar is seated in the another lateral slot and has another side edge and another width that is greater than the one width of the one bus bar. The locking member comprises a body having an inwardly facing outer locking surface engageable with the side edge of either one of the one and another elongated bus bars. The body of the locking member further has a first outwardly facing locking surface engageable with the one inwardly facing abutment surface on the one elongated support and a second outwardly facing locking surface engageable with the another inwardly facing abutment surface on the another elongated support, the first outwardly facing locking surface being between the inwardly facing outer locking surface and the second outwardly facing locking surface. The first and second outwardly facing locking surfaces on the locking member can be formed by grooves in a locking body while a flange on the body forms the inwardly facing outer locking surface. Through openings can be provided in the body of the locking member to reduce mass.